Optical Illusions: A Mystery for All Ages

An optical illusion is an optical phenomenon that results in an inaccurate or misleading impression. It is something that tricks us into perceiving something differently than its reality. In fact, some illusions show us one thing in an image, while someone else might see something completely different in the same image. Consequently, the word illusion comes from the Latin verb illudere which means "to mock."

Humans have five main senses - sight, hearing, taste, touch, and smell. Approximately seventy-five percent of the information humans obtain about our environment comes from our sight, making it the most vital of the five senses. The vision depends on the eyes to see and the brain to interpret what we see. The eyes have optic receptors known as rods and cones which enable sight. At the back of the eye, there is an optic nerve which connects to the brain's central nervous system. The brain receives stimuli (in the form of electrical impulses) from our eyes. These impulses are interpreted as sight. However, as was written in the excerpt of Lankavatara Sutra, "Things are not what they seem; nor are they otherwise." When the brain receives the image, it alters the initial perception of the image provided by our eyes. Sometimes, even the brain is deceived by information obtained by the eyes. Above all, how we perceive things has a direct relationship to how we react.

There are particular illusions that trick the human visual system into perceiving something that can't be seen, or into inaccurately perceiving what can be seen. There are many categories of optical illusions. Four of the main categories include distorting illusions, physiological illusions, paradox illusions, and fictional illusions. Distorting illusions are illusions caused by distortions of size, length, or curvature (the degree of curve). Physiological illusions are illusions that create effects on the eyes or brain due to the excessive stimulation of a specific type of characteristic such as brightness, tilt, color, movement, etc. Paradox illusions are illusions that are created by objects that are contradictory or impossible. Lastly, fictional illusions are illusions where one person might see one thing in the image, and then another person might see something entirely different than you even if it is the same image. There are many more types of optical illusions such as psycholinguistic illusions which pertain to the use of both parts of your brain. More importantly, there are numerous artists who create these illusions.

Roger Shepard is one of many artists who have created a great amount of optical illusions. Among them is his famous "Sara Nader" which he made in 1974. It is an optical illusion that fits under the category of fictional illusions. This illusion is in black and white. If only the white is viewed, a lady's face can be seen. If only the black is concentrated on, then a saxophone player can be seen.